Allergic rhinitis affects 20% of the population in the USA and has a serious financial impact in both lost time and medical costs for physician visits and medication. Currently, treatment falls into three categories. The first is to identify the allergen and develop a strategy of avoidance by the patient. The second strategy is the use of pharmacological agents to prevent symptoms and the third approach is desensitization to a specific allergen. The most cost-effective strategy is that of allergen avoidance and hence, there is substantial benefit for reliable assays that can detect the allergen to which a patient is sensitive. Because skin testing is unpleasant for the patient and requires significant physician involvement, radioallergosorbent tests (RAST) are the optimal strategy to identify allergic reactivities in atopic individuals. The focus of this proposal is to improve the sensitivity of automated in vitro testing for allergens by replacing an expensive detection reagent, a specific antibody to human epsilon heavy chains, with a low-cost high affinity bacterial IgE binding protein. The reagent will improve sensitivity and reduce false negative results for a key screening test to identify the causative agent of allergic responses in atopic individuals. PROPOSED COMMERCIAL APPLICATION: The commercial application of the technology is to replace an anti-IgE antibody with a higher affinity specific bacterial protein. This product will find applications in diagnostic allergy testing and may provide new strategies for developing a novel therapeutic to prevent allergic reactions in atopic patients.